Generally in polishing of a semiconductor substrate, such as a silicon wafer, not only improvement of surface quality in accordance with realization of higher performance and higher integration density of semiconductor devices but improvement of manufacturing efficiency for accommodating recent increases in demand is also considered to be an important theme. In order to respond to this theme, for example, piperazine is used for improving a polishing rate in a polishing composition disclosed in Patent Document 1.
However, a polishing pad used to polish a semiconductor substrate becomes clogged readily due to repeated use, and the clogging may reduce the processing efficiency of the semiconductor substrate and degrade the surface quality of the semiconductor substrate. When the polishing pad becomes clogged, the polishing process must be interrupted and removal of clogging by dressing or exchange of the polishing pad must be performed, thereby lowering the manufacturing efficiency of the semiconductor substrate. Therefore, for example with the polishing composition disclosed in Patent Document 2, a mixed solvent of water and alcohol is used for preventing aggregation and sedimentation of polishing particles in the polishing composition and suppressing precipitation of piperazine, which is used as a polishing promoter in the polishing composition.
However, clogging of the polishing pad occurs not only due to components in the polishing composition used but may also occur due to polishing debris generated from the semiconductor substrate by the polishing of the semiconductor substrate. With the polishing compositions disclosed in Patent Documents 1 and 2, it is difficult to prevent the clogging of the polishing pad caused by the polishing debris.